This invention relates to certain aromatic polyesters exhibiting desirable solubility characteristics and useful in the production of films and fibers. More particularly, it relates to aromatic polyesters containing recurring 2,2'-bis(trifluoromethyl)-4,4'-biphenylene radicals and to monomeric compounds useful in the production of such polyesters.
The production of polyesters, including aromatic polyesters, by the polycondensation of dicarboxylic acids (or the corresponding acyl halides) and polyhydric alcohols has been well known. For example, the production of such polyesters is described in U.S. Pat. Nos. 3,008,929 (issued Nov. 14, 1961 to E. A. Wielicki); in 3,786,022 (issued Jan. 15, 1974 to N. Hata et al.); in 4,066,620 (issued Jan. 3, 1978 to J. J. Kleinschuster); in 4,083,829 (issued Apr. 11, 1978 to G. W. Calundann et al.); and in U.S. Pat. No. 4,228,588 (issued Sept. 8, 1981 to J. A. Donohue). In general, it is well recognized that the mechanical and physical properties of polymeric films and fibers will depend upon the chemical structure of the polymers from which they are prepared and that such properties can be materially influenced by such molecular factors as chain stiffness, intermolecular forces, orientation and crystallinity. Accordingly, there has been considerable interest in the development of polyesters having particular structural or molecular configurations for the realization of one or more particular properties suited to a desired application.
In the production of polyester films and fibers, it will oftentimes be advantageous to prepare such films and fibers from a solution of the polyester in a common and readily available solvent material. Frequently, and particularly in the case of wholly aromatic polyesters, the polyester materials may be substantially insoluble. Moreover, the insolubility of the polyester may represent a limitation on the attainment of film- and fiber-forming molecular weights owing to the tendency of the polyester to precipitate from a solution polycondensation medium without attaining the requisite molecular weight for such film or fiber formation. Accordingly, the characteristic and advantageous properties of a polyester suited to a particular application will be more readily realized where the polyester material exhibits solubility in readily available organic solvents and can be polymerized to film- and fiber-forming molecular weights in such solvents.